Revealing Antifungal Activity Using the Poisoned Food Technique
Testing antifungal activity is an important step in determining a substance’s ability to inhibit fungal growth. One method that can be used is the poisoned food technique.
This method is widely used to evaluate the antifungal activity potential of natural substances, such as plant extracts and essential oils.
Table of Content:
- Understanding the Poisoned Food Technique
- Weighing the Advantages and Limitations of the Poisoned Food Technique
Understanding the Poisoned Food Technique
The poisoned food technique is an antimicrobial testing method primarily used to evaluate a substance’s antifungal activity. It is widely used in the preliminary screening of plant extracts and natural compounds with potential antifungal properties
The principle involves directly incorporating the test substance into agar medium before inoculating the microorganism. As a result, the fungus grows on a medium containing the test compound, allowing its antifungal activity to be observed and compared with a control medium that does not contain the antimicrobial substance
To evaluate its antifungal activity, the test begins by preparing agar media containing the test substance at specific concentrations, along with a control medium without the substance. Next, an agar plug approximately 3–6 mm in diameter containing the fungus is taken from the actively growing edge of the colony and placed at the center of a Petri dish
The edge of the colony is selected to obtain an inoculum with actively growing mycelium. All dishes are then incubated at a temperature and for a duration appropriate for the fungal species being tested.
After incubation, the colony diameters on the treatment and control media are measured to determine differences in growth. Antifungal activity in this method can be expressed as the percentage of colony growth inhibition.
It is calculated by subtracting the colony diameter in the treatment from that in the control, dividing the result by the control colony diameter, and multiplying by 100%. For example, if the colony diameter in the control reaches 60 mm, while the treatment colony measures only 15 mm, the percentage inhibition is 75%.
This result indicates that colony growth on the medium containing the test substance was inhibited by 75% compared with the control. This value reflects growth inhibition but does not directly prove that the test substance kills the fungus.
Samples that can be tested using this method include betel leaf extract, cinnamon extract, clove extract, plant essential oils, and synthetic antifungal compounds. For example, betel leaf extract can be incorporated into agar medium to evaluate its ability to inhibit the growth of molds such as Aspergillus or Fusarium, with the species selected according to the research objectives.
Testing can be performed at several concentrations to determine whether increasing the concentration leads to greater inhibition. The use of this method in natural product research is relevant for the preliminary screening of potential antifungal agents.
However, the fungal species, concentrations, medium, and incubation conditions must be determined according to an appropriate protocol.
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Weighing the Advantages and Limitations of the Poisoned Food Technique
One advantage of the poisoned food technique is that its procedure is relatively simple and allows several concentrations of a substance to be tested simultaneously. The method also produces quantitative data in the form of percentage inhibition, enabling comparisons of the antifungal activity of different samples.
Therefore, it is suitable for preliminary screening to assess the antifungal activity potential of both natural substances and synthetic compounds. However, the test results may be influenced by the solubility, stability, and ability of the test substance to mix uniformly throughout the agar medium.
Uneven distribution of the substance may affect fungal growth and lead to less accurate measurements. To minimize these effects, the test should include appropriate controls and be performed with multiple replicates.
Furthermore, this method measures inhibition based on colony growth and therefore cannot directly establish whether the test substance kills the fungus. A high level of growth inhibition does not necessarily indicate fungicidal activity, as the fungus may still be able to grow again after the antimicrobial substance is removed.
Therefore, further testing is required if the research aims to determine the minimum inhibitory concentration (MIC) or minimum fungicidal concentration (MFC).
Scientifically Validate Your Product’s Antifungal Efficacy Today!
Do not let the risk of fungal contamination compromise the quality, shelf-life, and reputation of your products. Ensure the effectiveness of the antifungal activity agents in your formulation is accurately validated using the Poisoned Food Technique.
Consult your microbiological testing needs with our independent analytical laboratory, IML Testing and Research. Obtain precise inhibition percentage data and launch your product backed by solid science!
Author: Dherika
Editor: Lina
References
Achar, P. N., Quyen, P., Adukwu, E. C., Sharma, A., Msimanga, H. Z., Nagaraja, H., & Sreenivasa, M. Y. (2020). Investigation of the Antifungal and Anti-Aflatoxigenic Potential of Plant-Based Essential Oils against Aspergillus flavus in Peanuts. Journal of Fungi, 6(4), 383. https://doi.org/10.3390/jof6040383.
Hossain, T.J. (2024). Methods for Screening and Evaluation of Antimicrobial Activity: A Review of Protocols, Advantages, and Limitations. European Journal of Microbiology and Immunology, 14(2), 97-115.
